Membrane Degassing - The Future Of Gas/Liquid Transfer

Contacting gas and liquids is essential for absorbing contaminants from gas streams, as in packed tower absorbers, or for removing contaminants from liquid streams, such as in air stripping of water and wastewater. What is needed for effective gas-liquid contact is high surface area between the gas and liquid, which enables the contaminants to transfer with minimal liquid-phase resistance.

Traditional methods of achieving this contact have been spraying of small diameter liquid droplets into the gas stream, bubbling the gas within the liquid using fine bubbles aerators, packed towers with media to spread the liquid as a thin film, or form droplets of liquid at projections within the contact media. In all cases, since the diffusivity of the contaminant within the liquid is several orders of magnitude smaller than in the gas phase, the liquid phase resistance is often the controlling factor. Hence, attempts have been made to create thin films of the liquid using gravity or liquid pressure.

Until now, the main issue with using sprays or packing media was their inability to handle particulates, which would either clog the spray head or deposit on the packing media, thereby increasing channeling and gas-phase pressure drop. Creating turbulence within the liquid by using venturi educators, fine droplet sprays or fine bubbles, or spreading the liquid as a thin film on a high surface area media, resulted in higher pressure drops for either the gas and/or the liquid, resulting in increased operating costs. In addition, high surface area medias are unable to handle particulates, scale and/or biological growth, which often occurs in systems handling wastewater.